From the core to the outskirts: structure analysis of three massive galaxy clusters

The hierarchical model of structure formation is a key prediction of the Lambda cold dark matter model, which can be tested by studying the large-scale environment and the substructure content of massive galaxy clusters. We present here a detailed analysis of the clusters RXCJ0225.9-4154, RXCJ0528.9-3927, and RXCJ2308.3-0211, as part of a sample of massive X-ray luminous clusters located at intermediate redshifts. We used a multiwavelength analysis, combining WFI photometric observations, VIMOS spectroscopy, and the X-ray surface brightness maps. We investigated the optical morphology of the clusters, we looked for significant counterparts in the residual X-ray emission, and we ran several tests to assess their dynamical state. We correlated the results to define various substructure features, to study their properties, and to quantify their influence on simple dynamical mass estimators. RXCJ0225 has a bimodal core, and two massive galaxy groups are located in its immediate surroundings; they are aligned in an elongated structure that is also detected in X-rays. RXCJ0528 is located in a poor environment; an X-ray centroid shift and the presence of two central BCGs provide mild evidence for a recent and active dynamical history. RXCJ2308 has complex central dynamics, and it is found at the core of a superstes-cluster. The complexity of the cluster's central dynamics reflects the richness of its large-scale environment: RXCJ0225 and RXCJ2308 present a mass fraction in substructures larger than the typical 0.05-0.15, whereas the isolated cluster RXCJ0528 does not have any major substructures within its virial radius. The largest substructures are found in the cluster outskirts. The optical morphology of the clusters correlates with the orientation of their BCG, and with the position of the main axes of accretion

Intrinsic myocardial recovery from the negative inotropic effects of acute hypercapnia

The inotropic effects of hypercapnia have been examined in the isometric papillary muscle preparation from the cat. The initial stage of depression which resulted from the acute induction of hypercapnia was followed by a significant degree of spontaneous recovery during the next hour. When the carbon dioxide concentration was returned to normal a temporary rebound in performance to well above control levels was observed. These findings are interpreted as being due to slow changes arising within heart muscle itself which partially compensate for the direct inotropic depressant effect of hypercapni

SARCS strong lensing galaxy groups: I - optical, weak lensing, and scaling laws

We present the weak lensing and optical analysis of the SL2S-ARCS (SARCS) sample of strong lens candidates. The sample is based on the Strong Lensing Legacy Survey (SL2S), a systematic search of strong lensing systems in the photometric Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). The SARCS sample focuses on arc-like features and is designed to contain mostly galaxy groups. We briefly present the weak lensing methodology that we use to estimate the mass of the SARCS objects. Among 126 candidates, we obtain a weak lensing detection for 89 objects with velocity dispersions of the Singular Isothermal Sphere mass model ranging from 350 to 1000 km/s with an average value of 600km/s, corresponding to a rich galaxy group (or poor cluster). From the galaxies belonging to the bright end of the group's red sequence (M_i<-21), we derive the optical properties of the SARCS candidates. We obtain typical richnesses of N=5-15 galaxies and optical luminosities of L=0.5-1.5e+12 Lsol (within a radius of 0.5 Mpc). We use these galaxies to compute luminosity density maps, from which a morphological classification reveals that a large fraction of the sample are groups with a complex light distribution, either elliptical or multimodal, suggesting that these objects are dynamically young structures. We finally combine the lensing and optical analyses to draw a sample of 80 most secure group candidates, i.e. weak lensing detection and over-density at the lens position in the luminosity map, to remove false detections and galaxy-scale systems from the initial sample. We use this reduced sample to probe the optical scaling relations in combination with a sample of massive galaxy clusters. We detect the expected correlations over the probed range in mass with a typical scatter of 25% in the SIS velocity dispersion at a given richness or luminosity, making these scaling laws interesting mass proxie

Analyse des propriétés statistiques des amas de galaxies

Les amas de galaxies constituent un des outils majeurs de la cosmologie moderne. Une mesure de l'abondance de ces objets permet de caractériser les propriétés cosmologiques de l'Univers et l'analyse de leurs différentes propriétés physiques telles que la masse, la température ou la luminosité X du gaz intra-amas permet quant à elle de contraindre les modèles de formation et d'évolution de ces objets. Dans les deux cas, la grandeur fondamentale est la masse de l'amas de galaxies. Être capable de les estimer de la manière la plus efficace et la plus précise possible est donc une nécessité. Le travail présenté ici s'inscrit dans cette optique : l'étude d'un échantillon représentatif d'amas de galaxies avec des masses déduites de deux analyses différentes afin d'en augmenter la fiabilité. Cette thèse met l'accent sur la méthode qui utilise les effets de lentilles gravitationnelles prédits par la théorie de la Relativité Générale. L'analyse d'images optiques grand champ des amas a constitué la plus grande partie de ce travail : sélection des galaxies lentillées, estimation de leur forme, mesure du signal de cisaillement gravitationnel et reconstruction de la masse. Chaque étape du processus s'accompagne d'erreurs et de limitations qui ont été mises en lumière, en particulier celles attribuées à la distance importante des amas. L'étude de l'échantillon d'amas du point de vue statistique a permis de caractériser ce qu'on appelle les lois d'échelle. Ces relations entre les différentes grandeurs des amas permettent d'étudier les modèles de formation des structures et constituent l'outil nécessaire à une utilisation des amas comme contrainte cosmologique. Leur étalonnage nécessite donc une estimation robuste des masses. Celles déduites de l'analyse des effets de lentilles gravitationnelles ont ains été comparées avec les résultats de la seconde méthode basée sur l'émission X du gaz intra-amas. Pour 7 des 11 amas de l'échantillon, les masses estimées sont compatibles ce qui augmente leur crédibilité. Pour les autres cas, les différences observées mettent en lumière les limitations intrinsèques à chaque méthode, en particulier les effets de projection et l'état dynamique de l'amas. Les résultats obtenus sur la calibration des lois d'échelles sont quant à eux en bon accord avec une grande partie des autres travaux du même type, notamment sur des amas plus proches. Par exemple, la présence de processus physiques non gravitationnels est mise en évidence, à la fois sur les propriétés du gaz et celles de la population des galaxies de l'amas.Galaxy clusters are one of the most powerful tool of modern cosmology. The abundance of these objects allows to characterize the cosmological properties of the Universe, and the analysis of their physical properties such as mass, temperature or X-ray luminosity of the intra cluster gas, allows to constrain models of formation and evolution of the galaxy clusters. In both cases, the fundamental property is the galaxy cluster mass. It is therefore mandatory to be able to measure it in the most efficient and accurate way. The work presented here follows this problematic: the study of a representative sample of galaxy clusters with masses derived from two different methodologies in order to increase their reliability. This thesis focuses on the gravitational lensing methodology as predicted by the theory of General Relativity. The analysis of the wide-field optical images has been the principal part of the work: selection of the lensed galaxies, estimation of their shape parameters, measure of the shear signal, and the clusters mass reconstruction. To each step of the process are associated errors and limitations, which were highlighted, in particular those due to the large distance of the clusters. The statistical study of the clusters sample allowed to characterize the so-called scaling laws. These relations between the several properties of a galaxy cluster can be used to constrain the model of formation and evolution of structures, and are the main tool used to derive cosmological constraints from galaxy clusters. Their precise calibration requires therefore robust masses. Those derived from the gravitational lensing effect have been compared with the results from the X-ray analysis. For 7 clusters over the 11 in the sample, the masses derived from the two methodologies are in good agreement, thus increasing their reliability. For the other clusters, the observed discrepancies highlight the intrinsic limitations of each method, in particular projection effects and the dynamical state of the cluster. The results obtained on the calibration of the scaling laws are in good agreement with numerous similar works, in particular at lower redshifts. For instance, the presence of non gravitational physical processes has been revealed, both on the properties of the gas and the galaxy population of the clusters

Cours complet de viticulture

2ème. éd, rev. et considérablement augm

Low X-ray Luminosity Galaxy Clusters. III: Weak Lensing Mass Determination at 0.18 << z << 0.70

This is the third of a series of papers of low X-ray luminosity galaxy clusters. In this work we present the weak lensing analysis of eight clusters, based on observations obtained with the Gemini Multi-Object Spectrograph in the $g'$, $r'$ and $i'$ passbands. For this purpose, we have developed a pipeline for the lensing analysis of ground-based images and we have performed tests applied to simulated data. We have determined the masses of seven galaxy clusters, six of them measured for the first time. For the four clusters with availably spectroscopic data, we find a general agreement between the velocity dispersions obtained via weak lensing assuming a Singular Isothermal Sphere profile, and those obtained from the redshift distribution of member galaxies. The correlation between our weak lensing mass determinations and the X-ray luminosities are suitably fitted by other observations of the $M-L_{X}$ relation and models

Dark matter-baryons separation at the lowest mass scale: the Bullet Group

We report on the X-ray observation of a strong lensing selected group, SL2S J08544-0121, with a total mass of $2.4 \pm 0.6 \times 10^{14}$ $\rm{M_\odot}$ which revealed a separation of $124\pm20$ kpc between the X-ray emitting collisional gas and the collisionless galaxies and dark matter (DM), traced by strong lensing. This source allows to put an order of magnitude estimate to the upper limit to the interaction cross section of DM of 10 cm$^2$ g$^{-1}$. It is the lowest mass object found to date showing a DM-baryons separation and it reveals that the detection of bullet-like objects is not rare and confined to mergers of massive objects opening the possibility of a statistical detection of DM-baryons separation with future surveys.Comment: 5 pages, 3 figures. Accepted for publication in MNRAS Letters. Typos correcte

Characterizing SL2S galaxy groups using the Einstein radius

We analyzed the Einstein radius, $\theta_E$, in our sample of SL2S galaxy groups, and compared it with $R_A$ (the distance from the arcs to the center of the lens), using three different approaches: 1.- the velocity dispersion obtained from weak lensing assuming a Singular Isothermal Sphere profile ($\theta_{E,I}$), 2.- a strong lensing analytical method ($\theta_{E,II}$) combined with a velocity dispersion-concentration relation derived from numerical simulations designed to mimic our group sample, 3.- strong lensing modeling ($\theta_{E,III}$) of eleven groups (with four new models presented in this work) using HST and CFHT images. Finally, $R_A$ was analyzed as a function of redshift $z$ to investigate possible correlations with L, N, and the richness-to-luminosity ratio (N/L). We found a correlation between $\theta_{E}$ and $R_A$, but with large scatter. We estimate $\theta_{E,I}$ = (2.2 $\pm$ 0.9) + (0.7 $\pm$ 0.2)$R_A$, $\theta_{E,II}$ = (0.4 $\pm$ 1.5) + (1.1 $\pm$ 0.4)$R_A$, and $\theta_{E,III}$ = (0.4 $\pm$ 1.5) + (0.9 $\pm$ 0.3)$R_A$ for each method respectively. We found a weak evidence of anti-correlation between $R_A$ and $z$, with Log$R_A$ = (0.58$\pm$0.06) - (0.04$\pm$0.1)$z$, suggesting a possible evolution of the Einstein radius with $z$, as reported previously by other authors. Our results also show that $R_A$ is correlated with L and N (more luminous and richer groups have greater $R_A$), and a possible correlation between $R_A$ and the N/L ratio. Our analysis indicates that $R_A$ is correlated with $\theta_E$ in our sample, making $R_A$ useful to characterize properties like L and N (and possible N/L) in galaxy groups. Additionally, we present evidence suggesting that the Einstein radius evolves with $z$.Comment: Accepted for publication in Astronomy & Astrophysics. Typos correcte